The present invention claims the benefit of Korean Patent Application No. P2001-81871 filed in Korea on Dec. 20, 2001, which is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) device, and more particularly, and to an LCD device and a method for fabricating the same, in which an adhesive power of upper and lower substrates is improved and a cell gap is uniformly maintained.
2. Discussion of the Prior Art
Generally, an LCD device is commonly used as a substitute for a cathode ray tube (CRT) because of its highs contrast ratio, suitability for displaying gray scales or moving pictures, and low power consumption. The liquid crystal display device for displaying images by external signals includes a thin film transistor (TFT) substrate, a color filter substrate, and a liquid crystal material layer. The TFT substrate has a TFT and a pixel electrode formed in each pixel region defined by gate and data lines. On the color filter substrate, a color filter layer and a common electrode are formed and the liquid crystal material layer is interposed between the two substrates. Presently, a spacer is inserted between the two substrates to leave a uniform space between them, and a sealant is formed along edges of the substrates to completely bond the two substrates together. The sealant prevents the liquid crystal material from flowing outside, and maintains a constant interval between the two substrates along a periphery of an active region.
A method for fabricating an LCD device according to the related art will be described below with reference to the accompanying drawings.
FIG. 1 is a cross sectional view of an LCD device according to the related art.
In FIG. 1, an LCD device includes upper and lower substrates 18 and 19 and a liquid crystal material layer 20 formed there between. A black matrix 11 for preventing a light leakage, a color filter 12 for displaying colors, and a common electrode 13 for applying a voltage to the liquid crystal layer 20 are formed on the upper substrate 18. Gate and data lines (not show) are formed on the lower substrate 19 and cross each other to define a pixel, a TFT 21 is formed at the crossings of the gate and data lines for switching a signal, and a pixel electrode 22 is formed on the liquid crystal material layer 20 forming an electric field by being provided with the signal from the TFT 21. In addition, an insulating film 27 is formed between the gate and data lines for insulating the gate and data lines from each other and a passivation film 28 is formed between the TFT 21 and the pixel electrode 22.
At this time, the gate insulting film 27 is deposited by a plasma enhanced chemical vapor deposition (PECVD) method using an inorganic material that closely adheres to the metal, and has an excellent insulating property, such as SiNx or SiOx, BCB or an acryl resin having a low dielectric constant property is used for a material of the passivation film 28. Additionally, a ball spacer 16 is inserted between the upper and lower substrates 18 and 19 and a seal pattern is formed on along the edges of the substrates for maintaining the interval of the two substrates.
In FIG. 2, the seal pattern is divided into an active seal pattern 14 and a dummy seal pattern 15. The active seal pattern 14 is formed along a circumference of an effective display area 13, thereby forming a cell gap and preventing a leakage of the liquid crystal material. The dummy seal pattern 15 is formed outside the active seal pattern 14, thereby absorbing vibrational shock generated during scribing and breaking process. The active and dummy seal patterns 14 and 15 are formed with an equal amount of a spray material, without being formed on an inlet 30 for the liquid crystal material. The active and dummy seal patterns 14 and 15 are formed by a screen printing method or a dispensing method using a thermosetting adhesive with a micro pearl material.
In FIG. 3. during the screen printing method, a screen mask 51 with a predetermined pattern is placed on the substrate 52, and a thermosetting adhesive 53 is dropped on the screen mask 51. Then, the thermosetting adhesive 53 is printed on the substrate 52 by a rubber squeezer. Accordingly, a seal pattern is formed on the substrate 52 as the thermosetting adhesive passes through the inlet of the screen mask 51.
During the dispensing method, the adhesive material is sprayed by compression of a sprayer filled with a thermosetting adhesive. Accordingly, a predetermined pattern is formed on the substrate to form a seal pattern.
In both methods, it is problematic to control the amount of spray material for forming the seal pattern. In addition, when the liquid crystal material is injected between the substrates, the liquid crystal material may leak through the space between the seal pattern and the passivation film 28 due to a lower adhesive strength of the sealant and organic insulating film.
In FIGS. 4A and 4B, a contact hole 29 is formed on the lower part of the active seal pattern 14. Accordingly, the active seal pattern 14 contacts the gate insulating film 12, thereby improving the adhesive strength of the sealant and organic irritating film.
In FIG. 4B, a step difference (bxe2x88x92a) is generated between the active and dummy seal patterns 14 and 15. Because of the step difference, intervals between the upper and lower substrates become uneven, and the liquid crystal material may flow outside the substrates since the active seal pattern 14 does not adhere to the upper substrate. Controlling the amount of spraying material can be one way to reduce the step difference between the active and dummy seal patterns 14 and 15. However, controlling the amount of spray material remains difficult.
Accordingly, the present invention is directed to a liquid crystal display device and a method for fabricating the same that substantially obviates one or more problems due to limitations and disadvantages of the prior art.
An object of the present invention is to provide an LCD device and a method for fabricating the same, in which a uniform cell gap is maintained and an adhesive strength between upper and lower substrates is improved.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, a liquid crystal display device, includes a substrate having an active region and a periphery region; an insulating film formed on the substrate; a passivation film formed on the insulating film and having a plurality of first and second contact holes formed along a circumference of the active region; a first seal pattern formed on the passivation film along a direction of the first contact holes; and a second seal pattern formed on the passivation film along a direction of the second contact holes.
In another aspect of the invention, a liquid crystal display device, includes a first substrate having an active region, a gate insulating film, and a plurality of thin film transistors; a second substrate having a color filter layer; a passivation film formed on the gate insulating film and having a plurality of first and second contact holes formed along a circumference of the active region, in which the first contact holes are located to the active region than the second contact holes; an active seal pattern formed on the gate insulating film within the first contact holes and on a predetermined portion of the passivation film; a dummy seal pattern formed on the gate insulating film within the second contact holes and on a predetermined portion of the passivation film; and a liquid crystal material layer formed between the first and second substrates.
In another aspect of the present invention, a method of fabricating a liquid crystal display device includes the steps of forming a gate insulating film and a plurality of thin film transistors within an active region of a first substrate, forming a passivation film on the gate insulating film and the thin film transistors, forming a plurality of first and second contact holes along a circumference of the active region by removing portions of the passivation film, forming an active seal pattern along a direction of the plurality of first contact holes and a dummy seal pattern along a direction of the plurality of second contact holes, and bonding a second substrate onto the first substrate.
It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.